Heretofore, a PZT (PhTiO3—PbZrO3) constituent-based ceramic containing lead has been used in a piezoelectric ceramic composition. The reason for it is that the aforesaid PZT, exhibiting excellent piezoelectric properties and a high mechanical quality coefficient, can readily produce materials exhibiting various desired characteristics which are required for various applications such as a sensor, an actuator, and a filter. Further, since the PZT has a high relative dielectric constant, it may also be used as a capacitor.
However, while the piezoelectric ceramic composition composed of the aforesaid PZT exhibits excellent characteristics, it contains lead as an element constituting the composition, leading to a concern that harmful lead is liquated from industrial waste of products containing PZT to result in an environmental pollution. The increasing awareness of environmental concern in recent years has made it difficult to manufacture the products containing substances such as PZT which have been a cause of environmental pollution. To cope with the above problem, piezoelectric ceramic compositions have been developed which include no lead in their compositions and whose main component is a chemical compound which is represented by formula {LiX(K1-YNaY)1-X}(Nb1-Z-WTaZSbW)O3, wherein x, y, z and w are within the ranges of 0=x=0.2, 0=y=1, 0<z=0.4, and 0<w=0.2, respectively (refer to Patent Document 1).
Technologies have been known in which at least one of any of metal elements selected from a group including Ag, Al, Au, B, Ba, Bi, Ca, Ce, Co, Cs, Cu, Dy, Er, Eu, Fe, Ga, Gd, Ge, Hf, Ho, In, Ir, La, Lu, Mg, Mn, Nd, Ni, Pd, Pr, Pt, Rb, Re, Ru, Sc, Si, Sm, Sn, Sr, Tb, Ti, Tm, V, Y, Yb, Zn, and Zr is added in an amount of 0.0005-0.15 mol/mol of the above-described main component in the piezoelectric ceramic composition in which the main component exhibits a perovskite structure of ABO3 type (refer to Patent Documents 2 and 3).
Patent Document 1: Japanese Patent Application Publication (hereinafter also referred to as JP-A) No. 2004-300012
Patent Document 2: JP-A No. 2004-244301
Patent Document 3: JP-A No. 2004-244300